Process of manufacturing portland cement



Patented Jan. 10, 1933 UNITED STATES PATENT" OFFICE,

JAMES H. COLTON, OF BERKELEY, CALIFORNIA, ASSIGNOR TO PACIFIC PORTLAND CEMENT COMPANY, CONSOLIDATED, A CORPORATION CALIFORNIA PROCESS OF MANUFACTURING PORTLAND CEMENT 80 Drawing. Original application filed February 4, 1926, Serial No. 86,097, now Patent No. 1,791,800.

Divided and this application filed This invention relates to a process of manufacturing Portland cement.

This application is a division of application Serial Number 86,097, filed February 4, 1926, now Patent No. 1,791,800.

An object of the present invention is to provide a process for manufacturing Portland cement by which the cement may be calcined and clinkered at lowertemperatures than can be employed under the standard methods of manufacturing Portland cement.

Another object of the present invention is to provide a process formanufacturing Portland cement which will produce a quickhardening cement producing high early ten. sile strengths and high early compression strength.

Another object of the present invention is to provide a process of manufacturing Portland cement with improved quick-hardening and high tensile and compression strength without changing the chemical analysis of the ordinary mix used in the production of standard Portland cement.

May 20, 1929.

Serial N 0. 364,707.

clinkered material.

In order to fully disclose the preferred method of practicing the present invention as well as disclose additional objects andadvantages Which will be derived by the method, a preferred example of a process of'manufacturing Portland cement embodying the present invention will be hereafter described.

'lhereis first produced a cement clinker by the use of such materials as are ordinarily employed in the making of Portland cement, that is to say, there is first prepared a. raw mix of such materials as lime rock and clay, or lime rock and shale, or marl and sea shells and clay, whereby the desired proportions of lime, silica and alumina, as well as .permissive quantities of iron, are present in the mix. The raw materiais used in the mix may be proportioned in any desired manner, for example by the use of the hydraulic index or I have discovered that if in the calcining ered' as in the ordinary process of producing of Portland cement, a quantity of previously calcined and ground cement clinker is added to the raw mix, the calcining of the mix may proceed at a'dower temperature than is usually necessary and the resultant cement clinker gives a higher early strength and possesses superior hardening qualities than the Portland cement resulting from the standard methods of production. The particular reasons why the addition of such pre-burned and ground clinker to the raw mix should produce these results is not definitely known but it is believed that the pre-burned, ground clinker acts as a catalyzer during the calcining operation and brings about a better combination of the calcium aluminum silicates present.

Apparently a Portland cement which produces high early tensile and compression strengths can be produced by clinkering a properly proportioned argillaceous and calcareous mixture grinding such clinker, again clinkering such ground clinkerand finally grinding such re clinkered material. Either all or only a portion'of the finished material Portland cement clinker. The clinker thus producedis then ground either with or without the addition of calcium sulfate, preferably the calcium sulfate not being added.

The ground clinker thus produced may then be returned to the kiln and reburnt to a point where it is again clinkered after which the twice clinkered material may then be ground and utilized in the usual manner to form a finished Portland cement.

As a modification of the process, I maytake the first produced clinker after the same is ground and add a portion of this ground clinker to auraw mix, such as generally employed in the making of standard Portland cement, for example, a mixture-of lime rock and clay, orlime rock and shale, or marl and sea shells and clay in proper proportions. While the invention is not limited to the employment of any minimum or maximum amount of this ground clinker which it is to be added to the raw mix previous to calcining and clinkering thelraw mix, I have obtained the best results by adding 20 per cent. of ground clinker to a properly proportioned mixture of raw materials as enumerated above of the proper analysis for the manufacture of standard Portland cement. I haveso far determined that favorable results may be obtained by using amounts of ground clinker varying from 5 per cent. to 25 per cent. and it appears that other percentages outside of this range would also produce favorable results.

After the ground clinker is added to the raw mix, it is then burned as is the standard Portland cement and processed in the usual manner to make a Portland cement, namely, by burning the mixture of raw mix and ground clinker to a clinker, grinding the clinker, and adding sufiicient calcium sulfate to give a required set.

By the .above method of manufacturing Portland cement, it is found that the raw mix is more readily clinkered, can be clinkered at a somewhat lower temperature, and the finished cement has increased strength and hardening properties over the standard Portland cement.

4. A process of manufacturing a Portland cement capable of setting to give high early compressive strength, comprising forming a normal Portland cement mix, burning said mix to produce a clinker, grindin the clinker, and recalcining the ground clin er to again clinker the material.

5. As an article of manufacture, a Portland cement capable of setting to give high early compressive strength, produced by burning a raw Portland cement mix including alumina, lime and silica to a clinker, grinding the clinker, and recalcining the same to again clinker the material.

Signed at San Francisco, Calif. this 25th day of April, 1929.

JAMES H. COLTON.

The Portland cement resulting from the process described herein is capable of producing extremely high compressive strengths particularly in short periods of time. For examplea 1: 3 mix of Portland cement 1%. (prepared in accordance with this invention) and sand, in comparison with ordinary commercial Portland cement B, tested under identical conditions gave the following results: Oompressice strength 1 :3 mix Age B 55 ostrength) 3 5061 (N 1300 7 6312 2400 28 7268 4150 2. A process of manufacturing Portland cement which comprises burmng a normal raw cement mix to a clinker, grinding the cllnker, and recalcining the same to again clinker the material.

v 3. A process of manufacturing a Portland cement possessing the property of setting to give high early compressive strength, com

prising forming a normal cement mix, burnmg said mix to a cllnker, grinding the clinker, then recalcining the ground clinker to again clinker the material, and finally grinding the recalcined' material. 

